The antigen/receptor specificity of antigranulocyte antibodies in patients with SLE.

The antigen/receptor specificity of antigranulocyte antibodies (AGAs) detected in the sera of patients with systemic lupus erythematosus (SLE) was investigated by inhibitory immunofluorescence test and Western immunoblotting technique. The interactions of AGAs with antigens of intact normal granulocytes were determined by inhibiting the binding of different myeloid monoclonal antibodies (mAbs). Seven of the studied 12 sera revealed binding to CD15 (X hapten) and/or to CD16 (FcR1o). The specificity investigation of AGAs was completed with Western immunoblotting technique. The binding of AGAs to bands with Mr of about 50-60 kDa and at 30 kDa on unstimulated granulocyte plasma membrane preparation could be demonstrated from 4 out of 6 AGA positive SLE sera. The cause of the disappearance of bands on the phorbol-myristate-acetate (PMA) activated membrane except those of the 50-60 kDa bands is still to be discovered.